DEC Rainbow 100, PDP-11 and Professional 380

Read in: IT 🇮🇹   EN 🇺🇸

At Varese Retrocomputing 2024, I had the pleasure of meeting Nicola Avanzi of RetroCampus, a retrocomputing enthusiast and expert. On this occasion, Nicola showed us three historical models of the Digital Equipment Corporation (DEC): the DEC Rainbow 100, the DEC Professional 380 and a scale replica of the DEC PDP-11/73.

Subscribe my YouTube channel ValorosoIT. Retro technology, vintage audio, retro computers, experiments and tests. Retroprogramming, Basic. Commodore, IBM, Atari, Apple, Texas Instruments, Amstrad, MSX.

During the interview, Nicola also presented a RAM expansion board, which he designed himself for the DEC Rainbow 100A. The result of historical research, the RAMbow allows you to
expand the first version of the Rainbow to 896Kb of memory.

Let's find out in detail these fascinating models and their technical characteristics.

DEC Rainbow 100: un computer innovativo di inizio anni '80

Il DEC Rainbow 100 è stato lanciato nel 1982, in un periodo cruciale per il mercato dei personal computer. La Digital Equipment Corporation, già famosa per i suoi minicomputer come il PDP-11, decise di entrare nel mercato dei PC, dopo il successo degli IBM PC. Tuttavia, DEC scelse un approccio differente, sviluppando un computer con un'architettura poco convenzionale.

DEC Rainbow 100, Autocad software, Digital Equipment Corporation, 80s, vintage computer

Il DEC Rainbow 100 è un sistema a doppio processore, con uno Z80 e un Intel 8088, capaci di eseguire, con la versione speciale di CPM 86/80, sia programmi a 8 bit (CP/M-80) sia a 16 bit (CP/M-86). I due processori comunicano tramite 62KB di memoria condivisa (dual port RAM) e utilizzano bus separati. Questo design permette al DEC Rainbow 100 di eseguire vari sistemi operativi, tra cui una versione MS-DOS speciale (non completamente compatibile con l'IBM PC), Concurrent CP/M 86, UCSD p-System e Venix.

Nicola showed us how this system can handle up to 896KB of RAM. This increase in RAM allows the DEC Rainbow 100 to run more demanding applications such as CAD and software development tools. During the interview, the computer was turned on and running Autodesk's popular AutoCAD software.

Another interesting feature of this computer is its drive, DEC RX50, which houses two 400KB floppy disks in a compact space, allowing you to access drives A: and B: alternately, using the same rotation shaft and a single head movement system.

DEC Professional 380: The power of PDP in desktop format

Alongside the DEC Rainbow 100, Nicola presented the DEC Professional 380, another DEC masterpiece. This line of computers, which includes the 325, 350 and 380 models, features the same chipset used in some of DEC's PDP-11 minicomputers, offering professional power and capabilities in a more compact and affordable package.

DEC Professional 380, Synergy 2, 80s, Digital Equipment Corporation, vintage computer

Il DEC Professional 380 è equipaggiato con un processore J-11 a 16 bit e un bus di indirizzo a 22 bit, il che gli consente di gestire fino a 4MB di RAM. Questa configurazione era decisamente avanzata per gli anni '80 e permetteva di eseguire applicazioni impegnative come il CAD e lo sviluppo software su vasta scala, rendendolo ideale per l’utilizzo in ambienti aziendali.

Follow me on Instagram channel. Retro technology, Commodore, vintage audio, retro computers, experiments and tests. Retroprogramming, Basic. Commodore, IBM, Atari, Apple, Texas Instruments, Amstrad, MSX.

Durante la dimostrazione, Nicola ha eseguito il Synergy 2.0, un ambiente per l'esecuzione delle applicazioni a finestre. Synergy permetteva di gestire più applicazioni contemporaneamente, come un foglio di calcolo, una calcolatrice e persino un gioco di scacchi. Una curiosità: l’interfaccia a finestre di Synergy non aveva il supporto del mouse e veniva utilizzata con la tastiera!

Replica of the DEC PDP-11/73... to scale

To complete the exhibition, Nicola showed a scale replica of the famous DEC PDP-11/73. This replica is based on the SIMH emulator, which runs on a Raspberry, offering a realistic simulation of the PDP control panel.

DEC PDP-11, PDP-11/73, Scale Replication, Raspberry, SIMH

Another alternative, to emulate the DEC PDP-11/73, is to use a Terasic DE0-Nano FPGA.

The original PDP is a complex and imposing system, but Nicola shows us a reproduction in a compact format, demonstrating how it is possible to relive the experience of these historic computers thanks to modern emulation.

The RAM expansion board designed by Nicola Avanzi for the DEC Rainbow 100

One of the most interesting parts of the interview was the presentation of the expansion board designed by Nicola for the DEC Rainbow 100A: the RAMbow v1.0. This card allows you to increase the RAM up to 896KB in the first version of the Rainbow which by its design was limited to a maximum of 256KB of RAM.
To do this, it was necessary to move the Intel 8088 processor from the motherboard to the expansion board itself. This technical solution allows you to take advantage of all memory address lines, even those that are absent on the expansion BUS.
Here is the link to the project: https://github.com/na103/rambow

DEC Rainbow 100, RAM memory expansion by Nicola Avanzi, 896 KB, Intel 8088, RAMbow v1.0

Subscribe to my channel and stay up to date

Se sei appassionato di retrocomputer e del mondo dell'elettronica vintage, non perdere queste esclusive retro-esplorazioni! Iscriviti al canale YouTube (@ValorosoIT) per accedere a esperimenti, interviste e a tutti i contenuti relativi ai retro computer. Sono presente anche su TikTok, Instagram, Facebook…

Subscribe my YouTube channel ValorosoIT. Retro technology, vintage audio, retro computers, experiments and tests. Retroprogramming, Basic. Commodore, IBM, Atari, Apple, Texas Instruments, Amstrad, MSX.

Posted in Retro Computer, Retro Technology and Vintage Electronics, All articles.

Leave a Reply

Your email address will not be published. Required fields are marked *